I can only speak from my own experience. Who's the best? Beats me, there are many good ones. But in terms of repairs, my best experience had been with Bryston. I had a 4B that needed repair. I shipped it to Bryston on Monday- it was literally back at my house on Friday. That's exceptional. Pass has also been exceptional in repairs.
I've had other gear repaired and typically I have gotten my gear back in 2-4 weeks. Only once did I have to send something back after repair because it still didn't work right. At least then the manufacturer paid for round trip shipping.
In terms of communication, I've had excellent experience with Pass Labs and Wyred 4 Sound. Others have been good to very good.
Only once did I buy a new piece of gear that was DOA. Frankly, I found that to be entirely unacceptable.